1. Field of the Invention
The present invention relates to a surface light source device and a liquid crystal display apparatus having the surface light source device. More particularly, the present invention relates to a surface light source device capable of decreasing channeling, and a liquid crystal display apparatus having the surface light source device as a light source.
2. Description of the Related Art
Generally, liquid crystal has both electrical and optical characteristics. An arrangement of the liquid crystal is changed in response to a direction of electric field applied to the liquid crystal. Light transmittance of the liquid crystal is changed by the arrangement of the liquid crystal.
A liquid crystal display (LCD) apparatus displays an image by using the liquid crystal. The LCD apparatus has various characteristics, for example, such as a thin thickness, a small volume and a lightweight compared with a cathode ray tube (CRT). Thus, the LCD apparatus is widely used for a portable computer, a communication device, a television set, etc.
The LCD apparatus includes a liquid crystal controlling part that controls a liquid crystal, and a light providing part that provides the liquid crystal controlling part with a light.
The liquid crystal controlling part includes a plurality of pixel electrodes that are formed on a first substrate, a common electrode that is formed on a second substrate, and a liquid crystal that is interposed between the pixel electrode and the common electrode. A number of the pixel electrodes is determined by a resolution. Each of the pixel electrodes is electrically connected to a thin film transistor (TFT), so that a pixel voltage is applied to the pixel electrode through the TFT. A reference voltage is applied to the common electrode. The pixel electrode and the common electrode include transparent conductive material.
The light providing part provides the liquid crystal with the light. The light generated from the light providing part passes through the pixel electrode, the liquid crystal and the common electrode to display an image. A display quality of the liquid crystal display apparatus is determined by a luminance and a uniformity of the luminance of the light. That is, when the luminance and the uniformity of the luminance of the light generated from the light providing part are increased, the display quality of the liquid crystal display apparatus is improved.
Generally, the light providing part may include a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED). The CCFL has various characteristics, for example, such as a high luminance, a long lifespan, a low heating value etc., and the LED has also various characteristics, for example, such as a low power consumption, a high luminance, etc.
However, the luminance of the CCFL and the LED is not uniform. In order to increase the uniformity of the luminance, the light providing part includes a light guide plate, a diffusion member, a prism sheet, etc.
When the light providing part includes the light guide plate, the diffusion member and the prism sheet, a size and a weight of a liquid crystal display apparatus are increased.
A surface light source device having a flat plate shape has uniform luminance. A conventional surface light source device includes a first substrate and a second substrate corresponding to the first substrate. A plurality of partition walls is disposed between the first and second substrates. The partition walls are disposed in substantially parallel with one another, and the partition walls are spaced apart from one another by a predetermined interval to form discharge spaces between the first and second substrates. A sealing member is disposed between the first and second substrates to isolate the discharge space from an exterior. A discharge gas is injected into the discharge space. Two electrodes that apply a voltage to the discharge gas are disposed on outer surfaces of the first and second substrates.
The partition walls are arranged so that the discharge spaces form a serpentine shape. The discharge spaces are connected to one another. That is, odd numbered partition walls have a first end portion that makes contact with the sealing member and a second end portion that is spaced apart from the sealing member to form a connection passage, and even numbered partition walls have a first end portion that is spaced apart from the sealing member to form a connection passage and a second end portion that makes contact with the sealing member.
When pressures of the discharge gas in the discharge spaces are different from one another, electric field strengths applied to the discharge spaces may be different from one another. When the discharge spaces are connected to one another by the connection passage, plasma may abruptly move through the connection passage to form a channeling between the discharge spaces. That is, when the electric field strengths are different from one another, densities of the plasma in the discharge spaces are different from one another so that a portion of the plasma moves toward one of the discharge space, which has lower density of the plasma, thereby forming the channeling. When the channeling is formed in the discharge spaces, the uniformity of the luminance is deteriorated.